The use of high pressure liquid applicator systems are generally known and have several uses. One such use is in the field of motor vehicle wash stations, particularly those of the self-serve variety. In these systems, a manually operated liquid applicator (usually called a "wand") is supplied with a stream of high pressure water (generated by means of a pump) so that the water is directed towards the motor vehicle by the user.
As may be appreciated, the washing of a motor vehicle usually involves several sequences. For example, the motor vehicle may first be rinsed with water discharged from the wand so as to provide a preliminary loosening of dirt and grime. This preliminary rinse sequence may then be followed by a wash sequence where a liquid detergent is supplied to the water and this high pressure liquid mixture of liquid detergent and water may then be directed towards the motor vehicle. Finally, any detergent residue which remains may then be removed by again directing a high pressure rinse water stream against the motor vehicle. It is also sometimes desirable to apply other chemical additives to the water stream at different sequences in the wash cycle. For example, a liquid wax or other surface protective medium may be injected into the water stream and thus applied onto the motor vehicle via the wand.
In the past, a user's selection of particular ones of these various liquid streams usually depended upon a manually actuated fluid switch which the user manipulated each time it was desired to change from one type of liquid stream (i.e. one which may or may not contain a chemical additive) to another. These fluid switches have typically been located within the motor vehicle wash bay or as a part of the wand itself (see, Trapp U.S. Pat. No. 3,850,371 ). These prior systems thus require that the user support the wand with one hand while attempting to manipulate the fluid switch with the other hand--an awkward exercise. And, since the wand itself may be somewhat cumbersome, it is usually insufficiently supported by the user during his/her switching from one liquid supply to another. This, in turn, may contribute to user fatigue.
In U.S. Pat. No. 4,290,442, a cleaning system is proposed whereby each initiation of flow from a source of water is sensed. An electrical signal is issued in response to each such flow initiaion. This electrical signal is then applied to a switching system which switches between one and another electrically-operated valves in response to receipt of each such electrical signal. In such a manner, sequencing of liquid from different sources is apparently possible.
Another system has been proposed in Norstrud U.S. Pat. No. 3,383,044 et al. According to this prior proposal, a hydraulically controlled pressure washer includes a pressure sensor so as to sense predetermined pressure conditions existing within a common supply line fluid-connected to a pressure wand. The pressure sensor activates one of a plurality of switches so as to select the injection of cleaning agents from either, or all, of such sources.
While the above-noted prior proposals may provide some benefit over strictly manual switching systems in terms of minimizing user fatigue and facilitating quicker selection between a number of liquid sources desired to be dispensed through the wand, some improvements are still required. For example, it would be desireable (in terms of liquid switching responsivenes) if a control scheme could be provided whereby each successive liquid to be dispensed would be in a "stand-by" mode while the previous liquid in the sequence is being dispensed. And, it would also be desireable if this stand-by condition became an active condition (i.e., so as to extablish fluid communication between the next successive liquid in the sequence and the wand) during a "no flow" condition through the wand. In this way, the lead time necessary for the next successive liquid to be discharged from the wand could possibly be minimized.
These objects are achieved according to the present invention by means which sense a predetermined pressure condition which occurs within the liquid supply line to the wand. This pressure condition is preferably indicative of a user's manual opening and closing of the wand. That is, means are provided in accordance with this invention for sensing the cyclical opening and closing of the wand by a user--which opening and closing respectively decreases and increases pressure conditions existing in the liquid supply line. In response to at least one of these sensed pressure conditions, valving structures are operated so as to open fluid communication between at least one liquid source and the wand and to close fluid communication between another liquid source and the wand. When the pressure condition is again sensed the fluid communication between the one and other sources and the wand is reversed--that is, fluid communication between the wand and the first source is closed and fluid communication between the wand and the other fluid source is opened.
As may be appreciated, any number of fluid sources containing (or adapted to be supplied with) the same or different liquids may be provided according to this invention and the supply of any particular liquid (or combination of liquids) may be selected by a user merely by changing the wand between its operable and inoperable modes (for example, as by merely cyclically squeezing and releasing the trigger of the wand).
Other advantages and aspects of this invention will become clear from the following detailed description of the preferred exemplary embodiment.